The Third International Symposium on Large Spatial Databases(SSD '93) was held at the National University of Singaporein June 1993. The previous meetings of the series were atSanata Barbara (1989) and Zurich (1991). The meetings areplanned as a forum for researchers and practitionersspecializing in database theory for and advancedapplications of Spatial Information Systems. This volume constitutes the proceedings of the symposium. Itcontains 25 selected papersand three keynotes papers:"Spatial data management in database systems: researchdirections" (W. Kim), "From extensible databases tointeroperability between multiple databases and GISapplications" (H. -J. Schek), and "The SEQUOIA 2000 project"(M. Stonebraker). The selectedpapers are collected intosections on: data modeling, spatial indexing, indexingmechanisms, handling of raster and vector data, spatialdatabase systems, topology, storage management, queryretrieval,knowledge engineering in SDS, and 3-dimensionaldata handling.